Gravity die casting of light metal frames



April 24, 1951 BRlDGE 2,550,037

GRAVITY DIE CASTING OF LIGHT METAL FRAMES Filed March 31, 1947 2 Sheets-Sheet l Inventor ARCH'IBALD c. BRIDGE By Attorney APril 1951 A. c. BRIDGE GRAVITY DIE CASTING UF LIGHT METAL FRAMES 2 Sheets-Sheet 2 Filed March 31, 1947 Inventor ARCHEBALD d. sRiDeE 1 llorney Patented Apr. 24, 1951 GRAVITY DIE CASTING OF LIGHT METAL FRAMES Archibald Claude Bridge, Westbridgeford, England, assignor to Luxfer Limited, London, England, a British company Application March 31, 1947, Serial No. 738,422 In Great Britain March 27, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires March 27, 1966 4 Claims.

This invention relates to light, metal frames.

In the manufacture of light, metal frames from non-ferrous aluminium alloys, heavy metal dies are employed which have to be machined, and to prevent the molten metal which is flowed in at about 720 C. from cooling to freezing point i. e. about 550 C., before the die is filled, the die has to be maintained at a high temperature.

Because of the mass of metal incorporated in the die, the latter has to be cooled by air streams directed on to it in an attempt to produce a chill effect i. e. rapid cooling, and then, of course, a large heat consumption is involved in restoring the die to that thermal state which will assure full flow of metal in the next pouring operation.

Unless chilling is efficiently effected, the casting produced is of poor mechanical strength and brittle.

A method of gravity die casting a light frame gravity die casting of of non-ferrous aluminium alloys according to the present invention is characterised by casting the metal in heated thin walled dies and allowing the molten metal to suffer a chilling effect by radiation from the die.

By such method of operation a good compact and ductile frame can be produced.

The method of gravity die casting according to the present invention is preferably further characterised by casting a second frame at the same time in a parallel die and so that the metal for the two frames is flowing in opposite directions at the same time, whereby the freshly poured metal of one frame imparts heat to the other to prevent freezing in each.

By such method of operation very considerablev saving in the costs of heating dies in gravity die castin operations is obtained.

The present invention also comprises a mul tiple die for gravity casting light, metal frames, such die comprising superposed thin metal elements, the transverse margins of which are shaped to correspond to a profile of the frame to be cast, fiat spacing elements disposed between the margins of the thin metal elements of progressively decreasing width downwards of the die, and similar spacing elements spaced inwardly from said margins disposed between the thin metal elements and of progressively decreasing width upwards of the die, whereby exactly similar castings are produced between each pair of the thin metal elements, the ingates of alternate thin metal elements being at one end of the die, and the ingates of the intermediate thin metal elements at the opposite end.

Preferably, however, the die is constituted by superposed continuous thin metal frames, each of which is shaped transversely to correspond .to a profile of the frame to be cast, the thin frames being spaced apart by fiat elements of progressively decreasing width downwards on the outer perimeter, and of a similar decreasing progression upwards on the inner perimeter of the multiple die, whereby exactly similar castings are produced between each pair of the thin frames, the ingates of alternateframes being at one end of the die and the ingates of the intermediate frames at the opposite end thereof.

From the foregoing it will be observed that in all constructions according to the present invention, there is, as compared with the solid metal dies at present in use, very little metal, because of the thin section of the dies, to be heated up during a flowing operation and consequently the moment the heat is removed rapid cooling by radiation can be effected and thereby the chill efiect assured.

Preferred constructions according to the pres,- ent invention comprise the combination with a multiple die including superposed continuous thin metal frames as just described, of means disposed within the casting frames for inducing an electric current through said frames whereby the frames are heated. From another aspect, therefore, the present invention comprises the combination with a multiple die including the aforementioned superposed continuous thin metal frames of a primary winding about one limb of a laminated core of U form, a removable yoke piece closing said. core, the secondary winding being constituted by the assembled thin metal frames when threaded over the core, whereby the multiple die becomes the secondary of an electrical transformer comprising the said primary winding and is heated by the current induced by the primary winding in its secondary.

Accordingly, the present invention also comprises a method of gravity die casting light, metal frames characterized by erecting a multiple die as a laminated structure and constituting it as a secondary of an electrical transformer.

In order that the invention may be more clearly understood some preferred embodiments as applied to the simultaneous casting of a plurality of light frames made of non-ferrous aluminium alloys will now be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 shows diagrammatically one form of cast light metal frame,

Figure 2 is a section on the line II-II, Figure 1,

Figure 3 shows diagrammatically a portion of a multiple die for casting frames as shown in Figure 1,

Figure 4 is a view looking in arrow A, Figure 3, and shows the arrangement of ingates in the die,

Figure 5 shows diagrammatically and to an enlarged scale a portion of an alternative form of multiple die, a

Figure 6 shows diagrammatically and to an enlarged scale a portion of a further alternative form of multiple die, and

Figure '7 shows diagrammatically an apparatus for heating a die. 7 j 7 Referring to the drawings, Figure 1 diagrammatically illustrates a light metal window frame to be cast in a die to be described below, the frame having a substantially Z-section as shown in Figure 2.

The multiple die diagrammatically illustrated in Figure 3 comprises superposed continuous thin steel frames I0 fabricated from sheet metal, for

example of 10 S. W. G. or from hot or cold rolled steel sections of suitable thinness, for example up to 4' thickness in the flange. The

superposed metal frames ID are each transversely shaped to form .a set so that they can n st one within the other but are spaced apart at the inner and outer peripheries to afford air spaces I l, i. e. casting cavities, between the superposed metal frames. 'The thin steel frames are each provided with transverse margins shaped to correspond to aprofileof the frame to be cast, the margins being connected by a web which, as shown in the drawing, is so disposed that its opposite surfaces form obtuse angles with the margins,

The spacing elements I 2 can be provided by attaching to the underside of each metal frame,

and in desired spaced relation, reinforcing frames of the same gauge sheet metal so that the air spaces II have a depth equal to the gauge of the metal employed in making the metal frames.

In such construction, the spacing elements may be themselves frame members l0 and be secured to the metal frames by spot welding .or riveting. Alternatively, as diagrammatically illustrated in Figure 5, the inner and outer edges Illa, l 0b of each metal frame may be folded under the metal frame to provide the spacing elements l2.

Figure 6 shows, diagrammatically, a multiple die the frames 10 of which are made of rolled located on one 'side'of the web and results in the casting of frames having a strengthened web section.

fl order that the cast frames shall each be of the direction of I the same cross-section, the spacing elements disposed between the margins of the thin metal frames, and which form with said margins the spaces to receive molten metal, are, considered in the direction of superimposition of the elements, of progressively decreasing width in one direction and of equal but progressively increasing width in the opposite direction, as indicated in the drawings, thereby between each pair of metal frames I0 air spaces ll of exactly similar cross-section are provided. Frames cast in multiple dies so constructed will then be capable of being fitted one inside the other, as is required in the case of a metal casement comprising a fixed outer frame having an inner frame hinged thereto. To obtain this result with the construction shown in Figure 6, the frames l0 are of identical crosssection and can, ifdesired, be located in position to form a multiple die by the use of spacing elements lZa, shown in chain line.

When it is desired that the cast frames shall be of the same size, the spacing elements on the outside and inside of the metal frames ID are of equal width so that the air spaces I l between the frames H] are of identical volume, and the cast frames produced by such a die will be identical in size and cross-section. w

In all instances suitable clamping means, not shown, are provided to retain the nested frames II] in relative position during casting and after the cast frames have cooled the clamps are removed so that the frames 10 can be lifted and the cast frames removed from the die.

Ingates 9, shown diagrammatically in Figure 4, are formed to alternate air spaces at one end of the multiple die and at the other end of the multiple die ingates to the intermediate air spaces are provided so that when the metal is flowed in at opposite sides of the multiple die the hot metal in each contiguous space is passing in opposite directions, as indicated by the arrows F, at the mid-way point of the die at which both streams of metal have lost a considerable proportion of their heat, which may have been reduced to 600 C., and would normally be approaching the freezing point of the metal, thereby precluding the metal from running further from this mid-way point, but onwards from this point they are passing into an area of the die which has been receiving heat from the freshly fed molten metal at a temperature of about Z20" C. with consequent increase in temperature conditions of the thin metal frames 10 and, accordingly, the elimination of any tendency for the metal to freeze.

However, the metal frames in may be heated up before a casting operation by disposing an assembly of nested metal frames in a muffle furnace or other oven but, as hereafter explained, it is preferred to provide heating means within the assembly of frames so that the heat so applied passes from the inside to the outside of the sheet metal frames. 7

-It will have been observed that in forming the metal frames ID, with the reinforcements or spacing elements Ii, hereinbefore described, that, in fact, a laminated structure is'obtained and experiments have shown that this structure can be constituted as the secondary to an electrical transformer.

To this end, the die can be coated with a suitable refractory lining, and a lubricant for the Accordingly, the assembly may, as diagrammatically shown in Figure '7, be threaded over a laminated core. l3. of a transformer which is 'of U shape but has a removable yoke piece 14 to permit the assembly to be threaded over the core, and the core is provided on the other limb to that on which the assembly is threaded with a primary winding I5, thereby, on passing current through the primary an induced current passes through. the assembly, heating the metal frames [0 from the inside outwardly, and experiments have shown that by such form of construction only the'amount of heat necessary to assure proper flow of the metal may be delivered to the assembly until the casting cavities are filled, and then the current cut off, allowing a rapid cooling. The cooling may, if desired, be augmented by flowing a cooling air stream across the assembly as will be well understood.

From the foregoing will be observed that thin metal frames, for instance frames of inch thickness and, for example, having a perimeter of 10 feet, can be accurately and easily cast, moreover, by suitably shaping the margins of the frames, a casting of predetermined profile can be obtained, in particular of Z-section, which is particularly useful in the manufacture of Window frames, or as frames for window openings, can be obtained.

To prevent oxidation of the metal frames Ill, they may each be provided with a protective coating, for example of alumina, in particular that composition known as micronised alumina.

An assembly of die frames l0 forming the laminated structure are entered in the transformer circuit with the yoke piece I4 removed, the yoke is then replaced and current switched on, and thermostatic means, not shown, may be provided for automatically cutting off the current when the multiple die has been raised to a suitable temperature. I

The metal is then poured into the hotassembly and after cooling has been effected, the yoke I4 is raised and the assembly of frames l0 removed and whilst the assembly so removed is cooling so that it can be handled, another assembly can be placed in the transformer circuit.

The castings are removed from an assembly by separating the metal frames when the solid cast frames are at once accessible for removal.

It may here be pointed out that in the casting of light frames of large size by existing solid metal dies that the metal shrinks on cooling and damaging stresses are set up in the casting by the die obstructing the shrinkage and, moreover, it-is extremely difficult to remove the castmg.

By employing a multiple die constructed according to the present invention, the casting is readily accessible for removal and the casting can be removed before the damaging stresses have set up.

By the present invention, a relatively simple means of casting light frames of non-ferrous aluminium alloys is achieved, the casting can be effected at relatively low cost and under precise temperature conditions so that an excellent type of product can be produced.

Moreover, processes of die casting according to the present invention are extremely economical in consumption of heat, and in labour expended in the actual casting operation and in the removal of the castings from the die.

Iclaim'f gravity die casting a light 1. A method of frame of non-ferrous aluminium alloy, comprisin the die by causing molten metal simultaneously to flow in opposite directions in successive spaces, and permitting the molten, metal to suffer a chilling effect by radiation from the die.

2. A multiple die for gravity die casting light metal frames, comprising in combination 'a'plurality of superposed thin metal frames each of which is shaped transversely to correspond to a profile of the frame to be cast, flat spacing elements to space said thin frames apart, the shaped surfaces of said thin frames and the inner end faces of the spacing elements defining a plurality of casting spaces for metal to be cast, said inner end faces at one side of the die being at progressively lesser distances from the said side and the inner end faces of the spacing elements at the opposite side of the die, considered in the same direction, being at progressively greater distances from said opposite side, and ingates formed by openings in the spacing elements to permit molten metal to be fed into the die, each ingate communicating with a casting space at a selected end of the die, the said thin metal frames permitting molten metal in the die to suffer a chilling effect by radiation from the die.

3, A multiple die for gravity die casting light metal frames, comprising in combination a plurality of superposed thin metal frames each of which is shaped transversely to correspond to a profile of the frame to be cast, flat spacing elements to space the frames apart, said spacing elements being integral with the frames extending from opposite surfaces thereof, the shaped surfaces of the thin frames and the inner end faces of the spacing elements defining a plurality of casting spaces for metalto be cast, said inner end faces at one side of the die being at progressively lesser distances from said side and the inner end faces of the spacing elements at the opposite side of the die, considered in the same direction, being at progressively greater distances from the said opposite side, and ingates formed by openings in the spacing elements to permit molten metal to be fed into the die, each ingate communicating with a casting space at a selected end of the die, the said thin metal frames permitting molten metal in the die to suffer a chilling effect by radiation from the die.

4. A multiple die for gravity die casting light metal frames, comprising in combination a plurality of superposed continuous thin metal frames each of which is shaped transversely to correspond to 'a profile of the frame to be cast, flat spacing elements to space the frames apart, the shaped surfaces of said thin frames and the inner end faces of the spacing elements defining a plurality of casting spaces for metal to be cast, said inner end faces at one side of the die being at progressively lesser distances from said side and the inner end faces of the spacing elements at the opposite side of the die, considered in the same direction, being at progressively greater distances from the said opposite side, and ingates formed by openings in the spacing elements to permit molten metal to be fed into the die, each ingate communicating with '7 V a casting space at a selected end of the the, the

said thin metal frames permitting molten metal inthe die to suffer a chilling effect by radiation from the die.

ARCHIBALD CLAUDE BRIDGE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 7 Number Number.

- x Name ""Date Spre'nger Feb. 18,1919 Myersv May 8, 1923 Beard 'Apr. 28, 1925 Chutter Apr. 1, 1930 Moore Oct. 4, 1932 Hoke Sept. 10, 1935 Hoke June 8, 1937 Goss Dec. 17, 1940 Hansen Sept. 9, 1941 FOREIGN PATENTS V Country Date Great Britain May 12, 1938 Germany Jan. 22, 1923 

